Method of treating wells



N 1940-\ P. .1. LEHNHARD, JR 2,221,261 METHOD OF TREATING WELLS I Filed May 2, 1939 'vae'n/w/me Marne/44 d N m R m wm Patented Nov. "12, 1940 UNITED .v STATES PATENT O E The invention relates to t he treatment of wells.

It more particularly concerns a method of treat--,.

ing wells with fluid agents whereby said agents,

may be introduced into a selected portion orsec'e. 5 tion of a formation penetrated by the bored 9.

well.

N a I -It is generally highly desirable in; treatingwells with fluid agents to-beable to direct the treatingfluid into only a selected section of the formation,

for otherwise it may be partially orcompletely wasted, and in some instances exceedingly deleterious efiects mayresult from the introduction .of the treating fluid into the wrong portion of the formation. For example, in treating-an oil well to seal or shut off a water-bearing stratum, contiguous an oil-bearing stratum with aJiquid sealing agent of the type which spontaneously solidifies, it is highly'desirable to direct the sealing solution into only the water-bearingstratum,

since its entry into and solidificationdn the oilbearing stratum would result in greatly curtailing, if not entirely stopping, the flow of the desired mineral fluid. .7

It is the conventional practice to. attempt to direct the treating fluid into the desired section of the formation by employing some form of packing device, or by maintaining thetreating fluid under a column-of an inert liquid,-such as, for example, oil. ,However, .neither of these,

methodsgive generally satisfactory results as regards ensuring that the treating fluid will be directed into only the selected stratum. Forex-.

ample, packing devices are notgenerally satisfactory because the contour of the well bore is usually highly irregular and oftentimes ends in a.

cavity which offers little or no opportunity for a packer to seat properly so as-to seal one portion of the well bore from another. :On the other hand, attempting to direct a treating .fluidinto 0 a selected stratum by maintaining it under a column of an inert liquid is not generally satisfactory because a portion of the formation adjacent the column of inert liquid may be porous, allowing fluid to drain thereinto, and this in turn al-v 5 ters the level at which-the treating fluid enters the formation.

It is, therefore, the principal object of the in vention to provide a-method of treating wells with fluid reagents whereby positive assurance is so had that the fluid enters only a selected section treating agent intoa wellthrough a conduit,-

the lower open endof which is located in a porous bed formed of granular material ,filling the well bore. adjacent the section-of the, formation v to be treated, while a quantityof ainon-pene 5 trating liquid mixture is maintainedupon the bed or body of porous material, a. fluid treating agent canj be-readily directed-into the selected section of the formation.

The term non-penetrating liquid mixture, as 10 used herein and in the appended claims, means aliquid mixture comprising a suspension ordlspersion of a material in a liquid which prevents the liquid-ffrom penetrating-porous formations, sucha's a body of sand, but of 'suflicientgfluidity 18 to be readily introduced into the well bore and removed therefrom- In the accompanying drawing forming Ta part of this;specificatiomjthe. single flgureis a dia-.

grammatic viewln vertical section of a well suit 20 ablyequipped for ,carrying out themethod of the invention. As v shown in the drawing, the upper portion-i of'ithe well bore is cased with a metal pipe 2, while the lower portion 3 of the well bore penetrates an oil' stratuml and ends; 25 in a. "water-producing stratum. 5. .Above the f ground level,'the well is shown equipped with" a casing head It throughwhich the tubing l2, provided with cap [8, extends into thewell. Pipe I3, c'ontrolled'by valve I communicates with the 30 well bore throughthe c sing head ,I I while pipe 15, controlled byvalve 16', communicateswith the wellbore through the tubihglZw The well tubing I2 is shown extending irito the wellto a point adjacent the water stratum 5, its lower perforate 35 end Il beinglocated in amass or body of granu- I ,lar material}, filling the,lower= portion of the well bore up to a levelr'l adjacent theupperportion of the water p'roducingstratum 5,.- The re-' 'mainder of, the lower. portion of the well bore 40 above the level I is; shown filled witha quantity of non-penetrating mixture. 8 up to a. level 9 adjacent the lowerend of the metal casing 2. vrEx-- terior of. the well tubing, the portion of thewell suring fluid Ill, such as oil. V, V The operation. of the method will be best 1111-; derstood from a description of a' treatment wherein a. sealing agent is to be introduced into only the water stratum 5, of the well bore is filled with a granular material, such as sand, flne gravel, or the like, form; ing a body .li'thereof, up to, a point 1 adjacent the upper level of the stratum" to be sealed oif. The 5 upper level of the granular material can be read 55 bore cased with metal pipe 2 is filled with a pres- The lower portion 3,,

ily determined, as by means of a measuring line carrying a suitable weight. After the requisite amount of granular material has been located in the lower portion of the bore, a quantity of a non-penetrating liquid mixture is introduced into the well through pipe [3, while valve I4 is maintained in an open position, in an amount the desired quantity of sealing agent has been i sufdcient to fill the well bore exterior of the tubing up to a point adjacent the lower end of metal casing 2. Thereafter the sealing agent is introduced into the well through pipe l5, while valve 16 is maintained in an open position, pressure being held upon the non-penetrating liquid mixture, as by means of introducing a volume of oil into the well through pipe [2. The liquid sealing agent is forced out through perforations in the lower end of the well tubing and permeates the porous granular mass 6, as well as the stratum to be sealed, but is prevented from rising inthe well bore above the level indicated at I by the non-penetrating liquid maintained under pressure upon the top of the porous material. After introduced, it may be displaced from the well tubing in any known manner, as by introducing a quantity of oil into the well tubing and applying pressure thereto. After the sealing agent has been allowed time to solidify, the well tubing may be pulledfrom the well, the non-penetrating liquid mixture removed from the well bore, as

by bailing.

It is to be understood, of course, that although it is usually preferable to employ only enough non-penetrating liquid mixture to fill the lower portion of the well bore up to the lower end of the casing, if desired the pressuring liquid used on top of the non-penetrating liquid may .bedispensed with and the entire well bore exterior of the tubing filled with the non-penetrating liquid mixture. a

If desired, the well tubing may be lowered into the porous mass after it has been properly located in the well bore.- i

Among the granular materials suitable for use in carrying out the method of the invention are sand, gravel, crushed rock, or the like. It is desirable to employ a material of such size that the void spaces between the particles are not large enough to permit ready penetration of the non-penetrating liquid 'mixture thereinto. If very coarse particles are employed, it is desirable to introduce a quantity of sand or the like on topof the coarse particles to keep the nonpenetrating-liquid from filtering away through the coarse material.

We have found that suitable non-penetrating liquid mixtures for our purpose consist of aqueous dispersions or solutionsof an organic jellifying material. The term-organic jellifying material as used herein means an organic material capable of being dispersed or dissolved in water to make a mobile liquid mixture, which exhibits jellifying characteristics after a time. The composition and source of suitable materials of this type are set forth in U. S. Patent No. 1,998,756. By mixing between about 0.1 and about 8.0 per cent, and preferably about 1.5to 4.0 per cent, of such an organic jellifying material with water, a non-penetrating liquid is obtained which will readily flow or can be pumped. Such a mixture will also withstand high pressures without penetrating a porous body of sand. A suitable material of this nature, having nonpenetrating characteristics when mixed with water, can be prepared from starches such as those of cassava or rice by mixing them with water to form a thin paste, and boiling the mixture until the starch is hydrolyzed. The cooked starch is dried at about 80 C. and the dried material ground, preferably to a fine powder. The powder so produced, when mixed with water in a concentration of from 1-8 per cent by weight, readily forms a substantially non-penetrating liquid mixture. Another liquid mixture having non-penetrating characteristics and of an inorganic type may be prepared by dispersing bentonite in water. By mixing from between about 1-5 per cent or more of bentonite in water, a non-penetrating liquid mixture is obtained which may be suitably'employed in accordance with the invention.

Although the method is particularly useful in connection with a treatment employing a liquid sealing agent of the type which spontaneously solidifies, such as for example, unpolymerized liquid styrene, unpolymerized liquid vinylidene chloride, and unpolymerized phenol formaldehyde resin-forming liquid, or the like, it may also be employed in carrying out a treatment with other types of chemical sealing agents such as those of the type which react with brines naturally present in the formation to produce sealing deposits, or with a solution introduced for the purpose. The method may also be suitably used to ensure the positive introduction of other treating fluids into only a selected portion of the formation, as for example, acids, paraflin solvents, and the like.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a method of treating with a fluid agent a selected section of an earth or rock formation penetrated by the bore of a well, the steps which consist in introducing said fluid agent into the well through a conduit, the lower open end of which is positioned in a bed of granular material located in the well bore adjacent the section to be treated, and maintaining a quantity of non-penetrating liquid mixture on top of the granular material-during the introduction of the fluid agent.

2. In a method of treating with a fluid agent a selected section of an earth or rock formation penetrated by the bore of a well, said well being equipped with the usual casing and tubing, the steps which consist in positioning the lower open end of the tubing in the well bore opposite the section to be treated, introducing into the well bore a quantity of granular material in an amount sufficient to fill the annular space between the well bore and the tubing adjacent the section to be treated, introducing into the well bore a quantity of anon-penetrating liquid mixture in an amount suflicient to fill the annular space between the well bore and the tubin up to the lower end of the casing, and thereafter introducing a fluid agent into the well through the tubing and thence into the formation while maintaining pressure upon the non-penetrating liquid mixture in excess of that employed toforce the fluid agent into the formation.

agent a'selected sectionof an earth or rock .for-

' ljmationfpenetratedbythe boreof a well, said well'being equipped-with the'usual casing and tubing, the steps which consist in positioning the lower open end of the tubing in the well bore opposite the section to be treated, introducing into the well bore a. quantity of sand in an amount sufficient to fill the well' bore exterior of the tubing up to the upper level of the section to be treated, introducing into the well bore a quantity of non-penetrating liquid mixture in an amount suflicient to fill the well bore exterior of the tubing upto the lower end of the casing,

and thereafter introducing the fluid sealing agent into the well through the tubing and thence into the formation whilemaintaining pressure upon'the non-penetrating liquid mixture in excess of that employed to force the sealing agent into the formation.

PHILIP J. LEHNHARD, JR. 

